The present invention relates to a method for restricting a telephone call in a key telephone or a private branch exchange (PBX) and, in particular, to a method by which a user can restrict the telephone call by directly installing a telephone call restricting code when the user intends to restrict a toll call or international call according to the class of extension line.
As to the restriction of a telephone call in general, class S makes all telephone calls available, class A makes only toll calls available, class B makes only local calls available and class C makes only extension calls available.
For the designation of extension class, the user can input a code or change the code by means of Man Machine Communication (MMC) which is performed by key programming. In the case of class A, however, it restricts only those numbers which begin with "0, 0". In the case of the class B, it restricts only those numbers which begin with '0".
The reason that input and correction are made possible by the MMC is that the correction and designation of a corresponding telephone call restriction class are made possible when the telephone call restriction program data fit for classes A-C is previously stored on a memory of key telephone and the operator carefully inputs those MMC keys in regular order according to a complicated method. Thereafter, the speaker can speak over the telephone according to the allow class permitted by the MMC. It is arranged that the speaker is unable to speak according to the other levels.
Although the telephone call restriction method by means of MMC make it possible to designate a class by previously storing a telephone call restriction code by class on the memory and by the MMC's designation of a complicated key, it is not a thing anyone can do easily. Restrictions placed as stated above will do in the case of domestic service. However, in case a class is changed by the MMC in a foreign country, programming by means of said MMC is impossible and programmed data must be stored by being changed so as to be fit for a corresponding code or class.